Advantages of the fibroin gene system are: 1) the coding sequence is simple, internally repetitious, and of unusually high G over C content, 2) a single gene comprises 0.004 percent of the genome, 3) fibroin mRNA comprises about 8 percent of the total transcripts synthesized in 30 min by the posterior silk glands of a mature larva of the silkworm Bombyx mori, and 4) isolated nuclei can also synthesize the mRNA in vitro in high proportion. In our initial studies we will isolate chromatin and RNA polymerase from silk glands, and determine whether the gene is transcribed faithfully. For the assay we will need to isolate the entire fibroin gene along with the presumptive promotor, initiator and terminator sequences. We will also need separated strands of fragments containing these sites. With these DNAs we can assay proper initiation and termination, and strand selectivity, and search for regulatory factors for faithful transcription of the gene. Therefore, initial studies include also the partial purification of the gene, cloning of the fibroin gene linked to a plasmid, and large scale production of the gene. Experiments are also planned to sequence the regions on either side of the gene which include the regulatory sequences, and to analyze interactions of these sequences with the putative regulatory factors. Our long-range objective is the in vitro reconstruction of the fibroin gene with its chromosomal proteins in order to reproduce the in vivo regulation.